1. Field of the Invention
The present invention relates to an imaging apparatus including a device that is configured to remove foreign substance adhering to a surface of an optical member.
2. Description of the Related Art
When a foreign substance such as dust exists in the vicinity of a focal plane of a photographing lens of a camera, a shadow of such foreign substance may undesirably be imaged by a solid-state image sensor. Such foreign substance may exist, for example, due to external entry of dust at the time of changing of lenses, or due to generation of fine abrasion powder of a constituent resin member of a shutter or a mirror, which occurs when the shutter or the mirror operates inside the camera.
Dust generated due to such causes may enter a space between a cover glass, which protects a solid-state image sensor, and an optical filter, such as an infrared-ray cut filter or an optical low-pass filter (LPF), disposed in front of the cover glass. In such a case, it may be necessary to disassemble the camera so as to remove the dust. Accordingly, it is extremely useful to hermetically seal a space between the cover glass and the optical filter for the solid-state image sensor so that dusts cannot enter the space.
However, when dust adheres to a side of the optical filter not opposing the solid-state image sensor, in the vicinity of a focal plane, a shadow of such dust may still be imaged by the solid-state image sensor.
Japanese Utility Model Application Laid-Open No. 06-063183 discusses a method for removing dust adhering to an object to be cleaned using an adhesive cleaning swab. In the method discussed in Japanese Patent Application Laid-Open No. 06-063183, the adhesive cleaning swab includes an adhesive member disposed at one end of a bar-like member via a cushion member and thus has a sufficient cushioning property and adhesive property. The adhesive cleaning swab is used to remove dust adhering to the surface of a cover glass or an optical filter for a solid-state image sensor.
Japanese Patent Application Laid-Open No. 2003-5254 discusses a method for cleaning a surface of a cover glass for a solid-state image sensor or an outermost surface of a hermetically-sealed structure with a wiper disposed on a shutter. With such a camera configuration, dust adhering to a surface of a cover glass for a solid-state image sensor or an outermost surface of a hermetically-sealed structure (e.g., a surface of an optical filter) can be removed without removing a lens or disassembling a camera. Japanese Patent Application Laid-Open No. 2004-172961 discusses a method for removing adhering dust by sliding an adsorbent cleaning film on the surface of a solid-state image sensor. With such a camera configuration, dust adhering to a surface of a cover glass for a solid-state image sensor or an outermost surface of a hermetically-sealed structure (e.g., a surface of an optical filter) can be removed without removing a lens or disassembling a camera. Japanese Patent Application Laid-Open No. 2004-172961 also discusses a method for cleaning the cleaning film using a brush.
In the method discussed in Japanese Utility Model Application Laid-Open No. 06-063183, dust can be readily removed from a surface of a cover glass surface or a surface of an optical filter for a solid-state image sensor if the amount of adhering dust is small. However, if the amount of adhering dust is large, it may be necessary to perform the dust-removing operation a number of times. In addition, if the adhesive cleaning swab contacts a portion other than the object to be cleaned inside a camera, inside portions of the camera may be contaminated. In addition, the adhesive cleaning swab may be inadvertently inserted into high-precision mechanical parts inside the camera.
Furthermore, in the method discussed in Japanese Patent Application Laid-Open No. 2003-5254, the same portion of a surface of a cover glass for a solid-state image sensor or an outermost surface of a hermetically-sealed structure is subjected to friction operations repeatedly in a state in which dust keeps adhering to the wiper. Accordingly, the cover glass surface or the outermost surface may be damaged. Moreover, dust adhering to the wiper may adhere again to the cover glass surface or the outermost surface.
In the method discussed in Japanese Patent Application Laid-Open No. 2004-172961, it is necessary for the size of a camera to be large because a space for winding the cleaning film is required. In addition, if the brush is merely disposed in the vicinity of the surface of a solid-state image sensor to be cleaned, dust that has once been removed from the solid-state image sensor with the brush may adhere again to the solid-state image sensor surface.